The global HIV/AIDS epidemic is stabilizing but at an unacceptably high level. It is now acknowledged that India is an epicentre of the HIV/AIDS pandemic. Counseling services is an important component which aims at creating awareness and promoting changes in reducing high risk behavior against HIV/AIDS. The objective of this study was to assess (KABP) regarding HIV/AIDS among pregnant women attending PPTCT program before and after counseling at Lok Nayak Hospital, New Delhi in India.It was an intervention longitudinal study. Data was collected by interviewing 600 pregnant women attending antenatal clinic during May 2006 to May 2007 using a pre-test and post-tested questionnaire. They were selected based on the eligibility criteria of gestational age between 5-32 weeks. The knowledge of pregnant women about AIDS was significantly different in pre-test (mean score =15) and post test (mean score=35) (P<0.000). Overall, condom usage among spouses of study participants significantly improved after counseling [241(47.3%) before and 345 (67.6%) after counseling] (P<0.05).